<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<!--标题标签
h1-h6表示标题标签从大到小
align:属性是对齐属性
left(默认)左对齐
center 居中
right右对齐
-->
<h1>标签1</h1>
<h2>标签2</h2>
<h3 align="center">标签3</h3>
<h4>标签4</h4>
<h5>标签5</h5>
<h6>标签6</h6>
</body>
</html>